Ultrahigh strain-response conductive polyurethane foam for strain sensor and pressure control switches

Conductive polyurethane foams as piezoresistive sensors have attracted considerable attention due to their promising applications in a variety of fields. However, there is still a challenge in high response to the strain of the conductive polyurethane foam. In this work, we constructed the high strain-response conductive polyurethane foam by immersing reduced graphene oxide and sodium alginate into the polyurethane foam. The high sensitivity of polyurethane foam to mechanical deformation was due to the change in the stacking degree of reduced graphene oxide induced by the deformation of polyurethane foam. The introduction of sodium alginate ensured the open pore structure and quick recovery of polyurethane foam. The polyurethane foam could achieve a good recovery of stress (98%) and the self-recovery was almost near to 100% after 5 min. Moreover, the conductivity of the reduced graphene oxide-loaded polyurethane foam was 0.013 S/m at 20% strain and 0.115 S/m at 70% strain. The high current sensitivity ranged from 13 µA to 100 mA corresponding to the strain ranging from 1% to 70%. The brightness of LED lamps was highly sensitive to the change of compressive strain, and the conductive polyurethane foam could accurately monitor the signal (bending of foam and bending of the elbow). Therefore, the conductive polyurethane foam should have broad application in various fields, for example, pressure control switches and strain sensors.